The natural follow-up.
13. d2d3 So far, natural play by both sides. Here Black has the option of immediately attacking the c4-knight, although this doesn't change the evaluation of the position (equality). 13... b8c6  14. a2a4 Keymer decides to secure the knight against b7-b5. 14... a7a6 And Praggnanandhaa decides to push b7-b5 anyway. 15. g2g3 This gives the queen a retreating square.